Are VOB-Files of joined DVDs will be recoded

Hi folks,

does someone know the following:

When I join 2 DVDs together and than use “Extract DVD” to get
the new joined structure. Does DVDRemake recode the VOB-Files?

The thing is. I have got 2 DVDs with a very high resolution movie on it,
like a HD-DVD and I don´t want a reduction in the resolution due to a new recoding. It´s not necessary to recode again.

Does anyone know?

Thanks for your advice.